The present invention relates to a method for manufacturing a heat insulating sash bar for window sash or, more particularly, to a method for manufacturing a heat insulating sash bar of which remarkably improved heat insulation is obtained between the face plates of the sash bar, one facing the inside of the room and the other facing the outside of the room, as connected with two connecting members made of heat insulating materials in such a manner as to form a hollow space surrounded by the face plates and the heat insulating connecting members.
As is well known, many of the modern window sashes are framed with sash bars made of a metal such as aluminum and shaped by extruding in the form of bar materials. When such window sashes are to be used in severe climatic conditions, there may be a problem in the use of an integrally shaped metal-made sash bar in respect of the heat insulation between inside of the room and outside of the room since the conduction of heat through the integrally shaped sash bars is not negligibly small due to the high heat conductivity of aluminum or the like metal of which the sash bar is made.
In this connection, it is desirable that the two oppositely positioned face plates forming the sash bar, one facing inside of the room and the other facing outside of the room, are not integral but isolated thermally from each other with connecting members made of a heat insulating sash bar is manufactured only with great consumption of time and labor in comparison with an integral metal-made sash bar which can be manufactured by a very efficient process of extrusion and the like alone and the dimensional accuracy of such a heat insulating sash bar is sometimes unsatisfactory depending on the skillfulness of the workers.